Microstructure evolution, mechanical properties, and fractography of AA7068/ Si₃N₄ nanocomposite fabricated thorough ultrasonic-assisted stir casting advanced with bottom pouring technique

Abstract

Ceramic particulate embedded aluminum metal matrix nanocomposites (AMNCs) possess superior mechanical and surface properties and lightweight features. AMNCs are a suitable replacement of traditional material, i.e., steel, to make automotive parts. The current work deals with developing Si3N4 strengthened high strength AA7068 nanocomposites via novel ultrasonic-assisted stir casting method advanced with bottom pouring setup in the proportion of 0.5, 1.0, 1.5, and 2 wt.%. Planetary ball milling was performed on a mixture of AA7068 powder and Si3N4 (in the proportion of 3:1) before incorporation in aluminum alloy melt to avoid rejection of fine particles. Finite element scanning electron microscope (FESEM), Energy dispersive spectroscopy (EDS), X-Ray diffraction (XRD), and Elemental mapping techniques were used in the microstructural investigation. Significant grain refinement was observed with increasing reinforcing content, whereas agglomeration was found at higher weight %. Hardness, Tensile strength, ductility, porosity content, compressive strength, and impact energy were also examined of pure alloy and each composite. Improvement of 72.71%, 50.07%, and 27.41 % was noticed in hardness value, tensile strength, and compressive strength, respectively, at 1.5 weight % compared to base alloy because of various strengthening mechanisms. These properties are decreased at 2wt.% due to severe agglomeration. In contrast, nanocomposite's ductility and impact strength continuously decrease compared to monolithic AA7068. Fracture analysis shows the ductile and mixed failure mode in alloy and nanocomposites.

Research progress on ceramic nanomaterials reinforced aluminum matrix nanocomposites

“…Properties of the nanocomposite has been reduced with 2 wt% of nano reinforcement in the alloy matrix due to the significant agglomeration of nanoparticles. Impact strength and ductility of nanocomposite have been continuously decreased as compared with pure metal [108]. Kumar et al reported cryo friction stir processing of stir casted aluminium nanocomposite specimens for the enhancemnet of mechanical properties due to the microstructural changes in the specimen.…”

“…al. [108]. Grain refinement has been improved with the reinforcement concentration in the aluminium domain, however, clustering of nanoparticles was observed with higher nanoparticle concentration.…”

“…Ceramic nanomaterials reinforced aluminium matrix nanocomposite possesses superior mechanical and surface properties with light weight feature. These advanced nanocomposite materials has the capability to replace conventional steel for automobile parts [108]. Combination of aluminium or its alloy and ceramic nanoparticle can provide a wide range of application in automobile, aerospace, defense, construction, agriculture, medical and other fields.…”

Investigation of Mechanical Properties and Microstructure of AZ31-SiC-Graphite Hybrid Nanocomposites Fabricated by Bottom Pouring-Type Stir Casting Machines

“…In vehicles and trucks, locomotives, and general aviation, AZ31 magnesium alloys have the potential to replace several standard structural materials as lightweight alloys [1][2][3]. In recent years, eforts have been undertaken to further enhance these alloys' characteristics by using reinforcements such as Si 3 N 4 [4], SiC [5], BN-WC [6], Gr-WC [7], TiC-TiB 2 [8], and titanium [9]. Due to modifcations in the mechanism of solidifcation for nanosized reinforcements, composites exhibit phenomenal results in terms of strength when nanosized particles are added to the matrix of magnesium.…”

Fabrication, Microstructure, and Mechanical Properties of AZ31/Silicon Carbide/Graphite Teinforced Hybrid Composites

“…Zang et al [11], investigated the AZ31/GNP composites produced by FSP, and found that the three multi-pass FSPs were necessary to produce defect-free composites with uniform GNP dispersion. The mechanical properties of the AZ31/silicon carbide composite have improved in comparison to the basic alloy, according to Kumar et al [12]. Kumar et al [13] discovered that the addition of SiC particles causes a considerable change in microstructure, lowers grain refinement, and improves mechanical properties.…”